The class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon is now well known in the art. These materials, also known as polyketones or polyketone polymers, are represented by the repeating formula ##STR1## wherein A independently is a moiety derived from at least one ethylenically unsaturated hydrocarbon. The polyketone polymers are typically produced by contacting the carbon monoxide and hydrocarbon monomers under polymerization conditions in the presence of a reaction diluent and a catalyst composition formed from a compound of a Group VIII metal, the anion of a strong nonhydrohalogenic acid and a bidentate ligand of phosphorus, arsenic, antimony, nitrogen or sulfur. Without wishing to be limited, a preferred class of catalyst compositions is formed from a bidentate ligand of phosphorus wherein the divalent group bridging the two phosphorus atoms is linear and has three carbon atoms, i.e., the bridging group is 1,3-propylene (trimethylene).
The use of bidentate phosphine ligands containing a bridging group other than 1,3-propylene is known. The nature of catalyst compositions containing such substituted 1,3-propylene bridging groups has been examined, particularly when the bridging group is substituted on the central carbon atom. See, for example, U.S. Pat. No. 4,877,861 and U.S. Pat. No. 4,933,311 as well as copending U.S. patent application Ser. No. 684,109, filed Apr. 12, 1991. In general, the catalyst compositions formed from bidentate phosphine ligands containing 2-substituted-1,3-propylene bridging groups do not provide advantages over the ligands without substituents other than hydrogen in either or both of the two most important consideration for the polymerization process, i.e., faster reaction rate or high molecular weight polymer. It would be of advantage to have an improved process for the production of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon which employs a bidentate phosphine ligand with a different type of substitution on the group bridging the two phosphorus atoms.